1. Field of the Invention
The present invention relates to a color cathode ray tube (CRT) and, more particularly, to a color cathode ray tube capable of reducing a damage rate of a panel due to a thermal impact in a furnace during a thermal treatment of a fabrication process, reducing a weight and enhancing a productivity.
2. Description of the Background Art
In general, a color CRT, a device for displaying images, is divided into two types of CRT: a curved-surface CRT and a flat CRT depending on an outer shape of a panel.
The curved-surface CRT having a curved outer surface is decreasing in its demand due to problems such as an image distortion and an eye fatigue due to a light reflection, while the flat CRT (FCD) is increasing in its demand thanks to its advantages that an image is not distorted, reflection by an external light is minimized and a visible region is maximized.
FIG. 1 is a side view showing the interior of the conventional color CRT.
As shown in FIG. 1, the conventional color CRT 10 includes a panel 1 having an effective surface coated with a fluorescent material 1a; a mask 2 having a color sorting function for electron beams made incident to the inner side of the panel 1; a funnel 3 coupled to a rear side of the panel 1 and maintaining the interior of the CRT in a vacuum state; a deflection yoke 5 for deflecting electron beams discharged from an electron gun 4; and a reinforcing band 6 engaged at a skirt portion 1b of the panel 1.
In the conventional color CRT constructed as described above, when an image signal is inputted to the electron gun 4, the electron gun 4 discharges electron beams, and the thusly discharged electron beams are accelerated and focused toward a fluorescent film 1a of the panel by virtue of a voltage applied from each electrode of the electron gun 4.
As the electron beams are deflected by the deflection yoke 5 and pass through a slot formed at the mask 2, a color sorting is made, and then, when the electron beams collide with the fluorescent material 1a of the inner surface of the panel 1, each fluorescent material is radiated to reproduce an image.
Since the interior of the color CRT is in the vacuum state by the panel and the funnel, the CRT receives a compression stress or a tensile stress at its the outer side and inner side. And in this case, if an excessive tensile stress is applied to a specific portion of a screen of the panel, a firecracker occurs to cause a big problem of a security.
Referring to the plane surface panel (FCD), its self-strength is weak, a shape of the panel is abnormal compared to a general panel, and a difference of thickness at a central portion and a corner portion is so big that it is disadvantageous for a heat distortion stress structure over a thermal expansion and explosion-proof characteristics, and thus its structural strength is degraded compared to the general curved-surface panel.
Therefore, in case of the conventional plane CRT, since its outer surface is almost flat while its inner surface is formed with a predetermined curvature, the thickness at the corner portion becomes thick to add the weight by as much as about 20%˜35% compared to the existing panel, and in manufacturing the panel, a tensile stress at a fused portion is increased due to a thermal impact in the furnace, causing a problem that the panel is increasingly damaged and a production yield of the panel is deteriorated.